Candidate. This K07 supplement will position Dr. Jacobs to continue towards independence as an investigator with expertise in developing and testing evidence-based interventions to improve patient and treatment-related outcomes across the cancer care continuum. Dr. Jacobs demonstrates promise as a clinical researcher, with substantial progress on her K07 thus far, and with additional training and mentorship will contribute to national and international efforts to reduce cancer burden and improve quality of life for survivors. Mentorship. The mentor team is comprised of internationally recognized investigators in supportive cancer interventions and health outcomes research (mentor: Jennifer Temel, MD), and treatment adherence in oncology and longitudinal adherence assessment (co-mentor: Joseph Greer, PhD). A scientific advisory committee with complementary expertise continues to provide guidance on: endocrine therapy (ET) and adherence in breast cancer survivors ([BCS] Ann Partridge, MD, MPH); survivorship and research ethics (Jeffrey Peppercorn, MD, MPH); mixed methods and qualitative analysis (Elyse Park, PhD, MPH); adherence intervention development (Steven Safren, PhD); and biostatistics (Nora Horick, MS). Training Plan. Dr. Jacobs will continue to achieve short-term goals through her coordinated research and training plan in (1) medical issues in ET and adherence for BCS, (2) adherence intervention development/health behavior change and e-counseling/telehealth, and (3) mixed methods and longitudinal adherence assessment. In addition to regular mentorship meetings and experiential training through the research plan, Dr. Jacobs will complete coursework and didactic trainings, attend and present at seminars and national conferences, and publish findings in peer-reviewed journals. Background. The majority of breast cancer is hormone sensitive and treated with 10 years of ET in order to reduce risk of recurrence and improve survival; however, adherence to ET among BCS is overwhelmingly poor, with half of women being non-adherent within five years. Furthermore, distressed BCS (e.g., related to side effects) are less likely to be adherent. There is an absence of efficacious interventions to improve ET adherence. Research Strategy. To address this gap, the study employs a mixed methods design to develop and test a videoconference, psychosocial intervention to improve adherence to ET, enhance symptom management, and reduce distress in BCS at Massachusetts General Hospital Cancer Center. Phase 1 included (1) intervention development with psychologists and oncology clinicians and semi-structured interviews with BCS (n=30), and (2) a pilot study to evaluate acceptability and refine the intervention (n=5). Phase 2 currently entails a pilot randomized controlled trial (n=75) to assess the feasibility of comparing the videoconference psychosocial intervention to a medication monitoring control on adherence outcomes over 6 months. This K07 lays the groundwork for an R01 to assess efficacy in a full-scale trial, and this supplement ensures Dr. Jacobs?s continuity as a researcher throughout her maternity leave and as she transitions back to full-time work.